1. Field of the Invention
The present invention relates to a control device. More specifically, the present invention relates to a control device that includes an electronic control unit which processes an electric signal from a sensor detecting a physical value, and outputs an electric signal to control a control target.
2. Related Art
For a certain control target, the electronic control unit that electrically controls this has not only the control target, but also various sensors for understanding the state of this control target, connected thereto. It goes without saying that high precision sensor outputs (physical values) are required in order to accurately understand the state of the control target and control the control target appropriately in response to this state on this occasion.
In addition, with the electronic control unit, it is not the analog sensor output itself, but rather a digital value obtained by A/D converting a differential output between the sensor output and ground that is supplied to arithmetic processing based on a control program. However, with electronic control units in an environment having a strong noise influence such as vehicles, the differential output will fluctuate if noise penetrates to the ground, and the accuracy of the A/D converted signal output will deteriorate. Therefore, various noise counter-measures have been considered (refer to Patent Documents 1 and 2).
For example, in Patent Document 1, a technology is disclosed that eliminates noise by electrically connecting an internal ground provided in a housing accommodating an electronic control unit for a vehicle, the housing and a vehicle body, and then providing a low pass filter between the electronic control unit and the power source.
In addition, Patent Document 2 discloses, as a noise counter-measure, a technology providing an electrostatic protection element between the ground for the electronic control unit and a case ground.
Patent Document 1: Japanese Unexamined Utility Model Registration Application, Publication No. S64-37345
Patent Document 2: Japanese Patent No. 4005794